


Family Instincts

by Tassledown



Category: Harry Potter - J. K. Rowling
Genre: Fiendfyre, Gen, Implied/Referenced Child Abuse, Inferi, The House of Black
Language: English
Status: Completed
Published: 2019-05-22
Updated: 2019-05-22
Packaged: 2020-03-09 18:49:51
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 2,204
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18922957
Author URL: https://archiveofourown.org/users/Tassledown/pseuds/Tassledown
Summary: James knows Sirius as a peer as strong, intelligent, and moral as he is himself. He doesn't often think of the difference their up-bringing makes, as it so rarely comes up. Who in their right mind would use the Dark Arts anyways?When it becomes necessary, even vital that Sirius do so - when no other option could help - what can James do?





	Family Instincts

**Author's Note:**

> Written mostly from pondering the House of Black, what makes the Dark Arts so dark, and how the Order copes with what Sirius' baseline spell knowledge truly contains.

"It looks like it was just a safehouse, there isn't much left now," James concluded. They were somewhere in the highlands in Scotland; it hadn't seemed likely to be much else, but the Order had gotten through the wards and one less house available to the Death Eaters was a small victory in a war going poorly. "What's behind that door?"

Sirius didn't look up from what he was doing; he was running a hand along the door frame, lightly touching various spots with a finger – his right ring finger, James noticed, and he guessed he was dotting the frame with blood.

"Sirius?" James prompted, hoping he wasn't distracting him too badly.

"What is it?" Gideon – or Fabian, James wasn't as good at telling them apart as Sirius was – came down from the loft.

"He's breaking a ward, I think." James said. "I don't know where the door goes."

"Probably a basement. I was just up in the loft. It's just a bedroom, although the door ward was obnoxious, I just broke the door handle."

Sirius abruptly stood up and stepped back, spelling the door to open with a triumphant noise. "Don't touch it but we can go through. I forced down the wards, it was easier..."

"What kinds of wards?" One of the Prewetts asked. "What do you think's down there?"

Sirius looked briefly thoughtful, "Something they needed to contain; there was a block to opening it from _inside_ as well, yes."

James pulled out his wand at that, but he followed Sirius and the Prewetts downstairs nonetheless, feeling the hair on his arms stand and shiver as he passed the open door.

The bottom of the stairs didn't improve matters. There were no overhead lights, so the Prewetts both raised their wands, strengthening the light they produced until it reached the corners of the room. Sirius had stopped in the middle of the room, looking uncertain.

"What was this?" James asked.

"Experimental magic," Fabian said. “Look, there’s a bunch of scrolls…”

There were tables along three walls, and quite a bit of free space around the edge of the room. The chains along the wall clinked softly as they moved, but they held nothing but empty air. The Prewetts were studying the tables, but Sirius was staring at the walls with a look of quiet focus.

It was strange, James thought, to see Sirius studying magic like that. He'd approached a lot of studying with that face, but James had rarely seen him using it in the field until Dumbledore had started sending them as backup to the Prewetts on reconnaissance missions.

"What are you looking at?" James asked. He tried to bring up the skill Sirius had started teaching him, to see or sense magic, but the room seemed to be soaked in it so much he couldn't tell where one spell started and the next begun.

One of the chains near them lashed out and Sirius took a step back, three feet away.

"Are you both done?" Sirius asked, and James took an involuntary step back from the wall as well, because Sirius' accent had become aristocratic again and that only happened when he was sincerely upset. "We should go..."

"There's a lot here, we should possibly bring Dumbledore back..." One of the brothers began.

The other suddenly dropped a scroll case with a shout and cursed.

Sirius whirled in place and stalked over. "What happened?"

"The case bit me --!"

The chains on the walls collapsed, limp, with a sound like metal rain.

Sirius went white, and shoved his wand back up his sleeve; James watched his face flush, his eyes livid, and he turned and raised his hands.

A wall of fire rose around them, racing from floor to ceiling in an instant, slicing through the tables and sending them crashing to the floor, razed in half. Heat seared James' face and the magic in question made his gut roil. He watched it writhe in a curtain around them, like a living thing and drew his wand. He held it on Sirius on instinct, confused until the spells in the room were ripped apart by the tongues of flame. The cloaking spell collapsed around them.

The room was _filled_ with inferi. The chains on the walls must have held them back, hidden to make them look like simply animate chains that might seize the unwary.

"Sirius," Fabian said. His voice was shaking. "What - how are you doing that - _Fiendfyre_ , is it _safe_ …?"

"You need to get out," Sirius said. His voice seemed oddly calm and he took a careful step back. "The stairs... are they clear?"

James looked back; the line of fire had touched the walls on either side, but as he watched an inferius touched the fire and shrieked as the leaping flames latched onto it with teeth and jaws; James' throat closed on his words with horror as he realized what Sirius had done.

"Yeah they are," Gideon said. "But you can't..."

"Get outside. James. _James_ ," Sirius said, and his voice was almost pleading. "Send your patronus when you're out, okay?"

Sirius took another careful step back, but he froze as the fire leaped, a gaping mouth snapping at Gideon’s hair. Sirius moved one hand, stiff with focus, and the semi-formed head turned with a shriek and consumed another inferius instead. James realized with sudden horror that Sirius wasn't going to be able to retreat with them, not and hold both the fire and the inferi off. What little he knew of fiendfyre was that it was often more dangerous to the caster than the observers.

"I won't -" James began, but the Prewetts didn't let him argue. The brothers took hold of his arms and dragged him up the stairs with them; dodging the basement door on the way out and through the front entry. They stopped outside the building and twenty feet away, but neither had let go of his arms.

"Should we apparate?" Fabian asked.

Gideon shook his head. "He won't know where we went. It shouldn’t be that dangerous, not yet."

"James," Fabian said. "Send it."

"We can't just _leave him_ ," James snarled. He jerked free of their grip, pulled out his wand and cast, thinking furiously… He hoped he knew what to say. He watched his patronus lope inside the house and desperately wished he could go after it.

 

The fury was stronger than fear. It always had been.

Sirius took another careful step back as the fire screamed and cackled in his ears. He could hear it, see it, _feel it_ , dancing over his skin, a physical thing tied so intimately to him it was hard to hold the line of where the fire began and he ended, as he hadn't let it _go_.

It was still _his_ , his fury that fed and shaped it, aimed solely at the deceptively clumsy figures on the far side of that wall of flames. He felt a giddy rush every time one of the inferi slipped too close and the fire ravenously devoured them; there were maybe only twelve left; it had started out fifteen, but each time he had had to close his eyes to master the rush.

Fury had been easy, in this house. His cousin's magic was all over it. The wards on the door were _hers_ ; a locked door upstairs defeated by a broken doorknob was _hers_. Bellatrix was nagging at his life and head and he was so very sick of it.

It was almost too easy; he took another step back and his focus slipped. A tendril of black flame crawled up his arm, a little snake baring its fangs, and Sirius shook it off in annoyance, unable to feel the pain of his flesh seared bright red with the fire still so closely tied. He couldn't let it go; couldn't release it, or let it go out, not until he knew they were out of the house.

The fire was giddy and hopeful; he laughed a little and took another step back towards the stairs.

A careless wizard thought you could cast fiendfyre and let it _go_ , let it play and do what it wanted, but you could never truly sever the link between yourself and the flames. It was fed by your fury, your rage, your desires and the one thing it truly wanted to devour over all others was _you_.

That had been lesson number one, he’d learned from his father: never cast a spell you don’t intend to own.

An inexperienced wizard thought that _casting_ fiendfyre was the hard part. It wasn't, not once you knew what to do. It was so very easy to raise fury, once you knew what you were doing. The right thought, the right memory, and you could be ready in moments.

That had been lesson number two, taught by a children’s book in the Black library: you have control of your emotions, and your emotions control your magic.

True control of fiendfyre was shown in _ending_ it, in severing your rage and letting it go, in keeping that spell so tightly under your control you knew that when you were done, it would be gone. _True_ control meant you could send it where you wanted it to go, no matter how long you'd held it raised.

Sirius hadn't summoned fiendfyre since he was twelve, under the shield and guidance of his father. The house wards had contained the fire until he could end it; he’d trusted his father for very little, but the one thing he’d known for sure was he’d never let his heir die.

The fire was _so_ hungry, Sirius could tell. It gnawed at his stomach like an ulcer, like starvation in the early days when you knew food was _just so close_ … If you just gave in, you could have it; just do what they wanted...

It slipped from his control, slithered out of his grasp briefly, and two more inferi screamed and turned to ash; the faces in the fire were becoming more defined, dragons and cockatrice, griffins and chimaeras, fiery tooth and claw seeking the wood on the walls and the bodies it knew were _just right there,_ so many dead, and one living… So close he could almost taste it…

He bit his lip so hard it bled, dragging them back under control. He almost didn't see the silver stag walk up to the side of his eyes and lower its head, watching him.

"Sirius," it said, in James' voice. "We're safe. Please come back, I'm scared for you."

 _Please come back_ , Sirius repeated his voice in his head as the patronus faded to silver stars.

 _Please come back_.

He exhaled, long and slow, but it was hard to drop the spell. He was scared, and fury was easier than fear. Fury kept him safe.

He clenched his left hand and felt the burned skin split, the blisters oozing and fluid drying instantly onto his raw skin.

 _He wasn't safe_. He just had to run faster than the monsters, right?

He could burn the inferi to ash, he knew. He could push it forward, end them all and he'd be able to walk up the stairs as calm as you could please. He _wanted_ them to burn, wanted that giddy feeling back, of knowing they were gone and the fire had taken another...

 _Please come back_.

He wouldn't be able to hold onto _himself_ if he tried.

The fury went out almost without him thinking about it. Sirius shifted as the wall of fire dropped, turning and darting up the stairs on four paws, faster than the inferi could register the fire had gone out, without the split-second warning of having shut down his rage. Padfoot dodged the door at the top of the stairs like it was another monster and skidded on the shined wood floor.

The house downstairs creaked and groaned; Sirius smelled smoke with no taint of sulphur and realized just how long he'd held the spell for. The walls of the house had started to combust from radiant heat. Padfoot knew to fear fire, in a place so deep Sirius might not have registered it himself. He hit the front door, raced to James and caught his robes, nearly dragging him off his feet as he tried to keep running.

The Prewetts drew their wands on him, surprised by the appearance of a black dog, and Sirius remembered to change back before they cursed him.

"The house is going to light up again, c'mon!" He shouted. "I don't know how bad! I haven't done that before!"

"You haven't _what_?" James shouted, but he was cut off as the house behind them cracked like an explosion and part of the roof dropped in with a shattering noise. Fire - gloriously red, ordinary fire - shot out of the hole that had opened clear to the sky.

Sirius clung to James' arm and started to laugh, giddy and exhausted, and James clung back. His friend, his brother in all but blood, was physically shaking, the whites showing all around his eyes as he took in what Sirius had done, and Sirius let him hold him because he needed the comfort too.


End file.
